Fully Integrated Thermal Accelerometer MXC6225XU

Transcription

1 Powerful Sensing Solutions for a Better Life Fully Integrated Thermal Accelerometer MXC6225XU Document Version 1.0 page 1

2 Features General Description Fully Integrated Thermal Accelerometer X/Y Axis, 8 bit, Acceleration A/D Output (± 2g) Absolute 0G offset less than +/- 50mg 4-position Orientation Detection Shake Detection with Interrupt Programmable Shake Threshold Shake Direction Detection I 2 C Interface Power Down Mode The MEMSIC Digital Thermal Orientation Sensor (DTOS) is the world s first fully-integrated orientation sensor. Its operation is based on our patented MEMS-thermal technology and is built using a standard 0.18um CMOS process. This sensor contains no moving parts (such as a ball) and thus eliminates fieldreliability and repeatability issues associated with competitive products. It also eliminates the click sounds typically heard in ball based orientation sensors. Shock survival is greater than 50,000g. This sensor detects four orientation positions, shake and shake direction. In addition, it provides X/Y axis acceleration signals with very low 0g offset. An I 2 C interface is used to communicate with this device and an interrupt pin (INT) is provided for shake and orientation. The device also has a power down enabled through the I 2 C interface. Shock Survival Greater than 50,000 g Operating Supply Voltage from 2.5V to 5.5V Produces no Mechanical Sounds ( click ) Package Size 3x3x1mm Applications Consumer: Functional Block Diagram Cell Phones Digital Still Cameras (DSC) Digital Video Cameras (DVC) LCD TV Toys MP3, MP4 Players Household Safety: Fan Heaters Halogen Lamps Iron Cooling Fans Figure 1 This sensor is packaged in a hermetically sealed 6-pin surface mount package (3 mm x 3 mm x 1mm); the product is RoHS compatible and operates over -20~70 C temperature range. Document Version 1.0 page 2

3 Electrical Specifications 1 Parameter (Units) Conditions Minimum Typical Maximum Operating Voltage Range (V) Supply Current (ma) 1 Turn-On Time (ms) X Operating Temperature Range (ºC) VDD Rise Time (ms) 2 10 Notes: 1 All specifications are at 3V and room temperature unless otherwise noted. 2 Maximum allowable power supply rise time from 0.25V to 2.5V (minimum). Slower VDD rise time may cause erroneous data retrieval from OTP memory at power-up. +Y Figure 2 Top View Sensor Characteristics 1 Parameter (Units) Conditions Minimum Typical Maximum Measurement Range (g) X/Y Axis ± 2.0 Alignment Error (º) X/Y Axis ± 1.0 ± 2.0 Sensitivity Error(%) X/Y Axis Sensitivity (LSB/g) X/Y Axis 64 Sensitivity Drift Over Temperature (%) Delta from 25 ºC (-20 ºC - 70 ºC) 15 Zero g Offset Bias Level (mg) X/Y Axis absolute value (-20 ºC - 70 ºC) dB Signal Bandwidth (Hz) 10 Notes: 1 All specifications are at 3V and room temperature unless otherwise noted. Figure 3 Bottom View Pin Description: LCC6 Package Pin Name Description 1 INT This pin is the DTOS interrupt output. The logic level on this pin reflects the state of the INT bit in the STATUS register. INT is set when the orientation differs from the last orientation read by the processor, or a shake event is detected. INT is cleared upon the read of the STATUS register. 2 NC During normal operation, this pin should be left floating. Figure 4 3 VDD This is the power supply input for the DTOS. The DC voltage should be between 2.5 and 5.5 volts. 4 I 2 C SCL This pin is the serial clock line for the I 2 C interface on the DTOS. Since the DTOS only operates as a slave device, this pin is always an input. LCC6 Package Drawing Package Thickness: 1.05mm +/- 0.1mm 5 I 2 C SDA This pin is the serial data line for the I 2 C interface on the DTOS. It is an I/O pin that functions as an input during a write to the DTOS, and an output during a read from the DTOS. 6 GND This is the ground pin for the DTOS. Document Version 1.0 page 3

4 Circuit Schematics Figure 5 Note: R1 and R2 are pull-up resistors, the value can be determined by customer INT does not need any pull-up/pull-down resistor If INT is not used, just keep it disconnected, don t pull up or pull down Landing Pattern Figure 6 Document Version 1.0 page 4

5 Digital Parameters Symbol Parameter (Units) Minimum Typical Maximum VIH High Level Input Voltage (Volts) 0.8*VDD VIL Low Level Input Voltage (Volts) 0.2*VDD Hysteresis of Schmitt Trigger Input (Volts) 0.1 IIL Input Leakage, All Inputs (ua) VOL Low Level Output Voltage (Volts) 0.4 Digital Switching Characteristics Symbol Parameter (Units) Minimum Typical Maximum tr Rise Time (us) 0.3 tf Fall Time (us) 0.3 f SCL SCK Clock Frequency (khz) td1 SCL Low Time (us) 1.3 td2 SCL High Time (us) 0.6 td3 Data Hold Time (us) td4 Data Set-Up Time (us) 0.1 td5 Start Set-Up Time (us) 0.6 td6 Start Hold Time (us) 0.6 td7 Stop Set-Up Time (us) 0.6 td8 Bus Free Time Between Start and Stop (us) 1.3 Figure 7 Document Version 1.0 page 5

6 Orientation Characteristics Orientation State Bits OR [1,0] DTOS Output state response to orientation If the sensor is rotated past the 45 degree threshold, the orientation bits will change only if the sensor stays in the same state for a defined period of time. If the sensor crosses back before this time period, the orientation bits remain unchanged. This is to prevent dithering of the orientation state. Four user programmable hysteresis time periods are available : 160, 320, 640 and 1280ms Ф=0 Off-axis operating range for orientation -60 deg +60 deg a x = -a y Region III OR[1:0]=10 a y Region II OR[1:0]=01 Region I OR[1:0]=00 a x = a y angle threshold θ=45 degree a x Figure 8-90 deg Y Axis +90 deg Region IV OR[1:0]=11 Figure 9 Figure 10 Front View - + Ф Same Plane Side View DTOS is guaranteed to detect orientation changes with up to 60 degrees of off-axis tilt θ + DTOS Shake Detection Shake and shake direction are orthogonal to screen orientation. An interrupt pin (INT) is set high and must - Orientation Angle Figure 12 Off-Axis Tilt be cleared by the MCU via the I 2 C interface. Four user programmable thresholds are available: 0.5g, 1g, 1.5g and 2g. Figure 11 Document Version 1.0 page 6

7 DTOS I 2 C Interface A slave mode I 2 C interface, capable of operating in standard or fast mode, is implemented on the DTOS. The interface uses a serial data line (SDA) and a serial clock line (SCL) to achieve bi-directional communication between master and slave devices. A master (typically a microprocessor) initiates all data transfers to and from the device, and generates the SCL clock that synchronizes the data transfer. The SDA pin on the DTOS operates both as an input and an open drain output. Since the DTOS only operates as a slave device, the SCL pin is always an input. There are external pull-up resistors on the I 2 C bus lines. Devices that drive the I 2 C bus lines do so through open-drain n-channel driver transistors, creating a wired NOR type arrangement. Data on SDA is only allowed to change when SCL is low. A hi to low transition on SDA when SCL is hi is indicative of a START condition, whereas a low to hi transition on SDA when SCL is hi is indicative of a STOP condition. When the interface is not busy, both SCL and SDA are hi. A data transmission is initiated by the master pulling SDA low while SCL is hi, generating a START condition. The data transmission occurs serially in 8 bit bytes, with the MSB transmitted first. During each byte of transmitted data, the master will generate 9 clock pulses. The first 8 clock pulses are used to clock the data, the 9th clock pulse is for the acknowledge bit. After the 8 bits of data are clocked in, the transmitting device releases SDA, and the receiving device pulls it down so that it is stable low during the entire 9th clock pulse. By doing this, the receiving device acknowledges that it has received the transmitted byte. If the slave receiver does not generate an acknowledge, then the master device can generate a STOP condition and abort the transfer. If the master is the receiver in a data transfer, then it must signal the end of data to the slave by not generating an acknowledge on the last byte that was clocked out of the slave. The slave must release SDA to allow the master to generate a STOP or repeated START condition. The master initiates a data transfer by generating a START condition. After a data transmission is complete, the master may terminate the data transfer by generating a STOP condition. The bus is considered to be free again a certain time after the STOP condition. Alternatively, the master can keep the bus busy by generating a repeated START condition instead of a STOP condition. This repeated START condition is functionally identical to a START condition that follows a STOP. Each device that sits on the I 2 C bus has a unique 7 bit address. Document Version 1.0 page 7

8 The first byte transmitted by the master following a START is used to address the slave device. The first 7 bits contain the address of the slave device, and the 8th bit is the R/W* bit (read = 1, write = 0; the asterisk indicates active low, and is used instead of a bar). If the transmitted address matches up to that of the DTOS, then the DTOS will acknowledge receipt of the address, and prepare to receive or send data. If the master is writing to the DTOS, then the next byte that the DTOS receives, following the address byte, is loaded into the address counter internal to the DTOS. The contents of the address counter indicate which register on the DTOS is being accessed. If the master now wants to write data to the DTOS, it just continues to send 8-bit bytes. Each byte of data is latched into the register on the DTOS that the address counter points to. The address counter is incremented after the transmission of each byte. If the master wants to read data from the DTOS, it first needs to write the address of the register it wants to begin reading data from to the DTOS address counter. It does this by generating a START, followed by the address byte containing the DTOS address, with R/W* = 0. The next transmitted byte is then loaded into the DTOS address counter. Then, the master repeats the START condition and re-transmits the DTOS address, but this time with the R/W* bit set to 1. During the next transmission period, a byte of data from the DTOS register that is addressed by the contents of the address counter will be transmitted from the DTOS to the master. As in the case of the master writing to the DTOS, the contents of the address counter will be incremented after the transmission of each byte. The protocol for multiple byte reads and writes between a master and a slave device is depicted in Figure 13. Figure 13 The I2C address for DTOS is set as 2AH. Document Version 1.0 page 8

9 User Register Summary Address Name Definition Access Contents Stored in OTP Memory $00 XOUT 8-bit x-axis acceleration output $01 YOUT 8-bit y-axis acceleration output $02 STATUS orientation and shake status $04 DETECTION Power down, orientation and shake detection parameters read read read write no no no no The registers available to the user on the DTOS are summarized in the table above. Each register contains 8 bits. $00: XOUT 8-bit x-axis acceleration output (read only) D7 D6 D5 D4 D3 D2 D1 D0 XOUT[7] XOUT[6] XOUT[5] XOUT[4] XOUT[3] XOUT[2] XOUT[1] XOUT[0] 8-bit x-axis acceleration output. Data in 2 s complement format with range of -128 to $01: YOUT 8-bit y-axis acceleration output (read only) D7 D6 D5 D4 D3 D2 D1 D0 YOUT[7] YOUT[6] YOUT[5] YOUT[4] YOUT[3] YOUT[2] YOUT[1] YOUT[0] 8-bit y-axis acceleration output. Data in 2 s complement format with range of -128 to $02:STATUS orientation and shake status register (read only) D7 D6 D5 D4 D3 D2 D1 D0 INT SH[1] SH[0] TILT ORI[1] ORI[0] OR[1] OR[0] OR[1:0] is a 2-bit indication of the device orientation, according to the following scheme: OR[1:0] = 00 device is vertical in upright orientation; 01 device is rotated 90 degrees clockwise; 10 device is vertical in inverted orientation; 11 device is rotated 90 degrees counterclockwise. The bits OR[1:0] are indicative of long-term orientation. The orientation is determined by measuring the signs of the quantities ax ay, and ax + ay, as shown in Fig. 10. In addition to these measurements, the orientation measurement must be validated by requiring that the larger in magnitude of ax, ay be greater than 3/8 g. In order for a new value of OR[1:0] to be written to the STATUS register, a valid measurement of the new orientation must be measured a consecutive number of times determined by the setting of bits ORC[1:0] in the DETECTION register. This provides a low-pass filtering and hysteresis effect that keeps a display from flickering near orientation boundaries Document Version 1.0 page 9

10 ORI[1:0] is the instantaneous device orientation. It follows the same scheme as OR[1:0], except that it is updated every time a valid orientation measurement is made, not subject to the same low-pass filtering as OR[1:0]. TILT is an indication of whether there is enough acceleration signal strength to make a valid orientation measurement. If TILT = 0, the orientation measurement is valid, if TILT = 1, then the orientation measurement is invalid. TILT is updated every measurement cycle. SH[1:0] indicate whether a shake event has taken place, and if so, its direction. Shake can only be detected in a direction perpendicular to the vertical orientation of the device. When an acceleration perpendicular to the device orientation (ax for OR[1:0] = 01 or 11; ay for OR[1:0] = 00 or 10) is sensed that has a magnitude greater than the value set by bits SHTH[1:0] in the DETECTION register, then shake detection begins. For a shake event to be written to SH[1:0], the perpendicular acceleration must again exceed the magnitude set by SHTH[1:0] but with the opposite sign (if bit SHM = 0 in the DETECTION register), or just reverse its sign (if bit SHM = 1 in the DETECTION register). The above mentioned second acceleration events must occur within a certain amount of time, set by SHC[1:0] in the DETECTION register, of the original breaking of the threshold. If a shake is determined to have occurred, then the direction of the shake can be determined by the signs of the accelerations. The shake status is indicated as shown in the following table: SH[1] SH[0] 0 0 no shake event 0 1 shake left 1 0 shake right 1 1 undefined INT is the interrupt bit. Setting this bit hi will cause the INT pin to output a hi level. The INT bit will be set whenever, 1. The orientation, as indicated by bits OR[1:0] changes, or 2. A shake event occurs. The microprocessor can then service the interrupt by reading the STATUS register. Once a shake event occurs, no new shake events will be recorded until the interrupt has been serviced, although the orientation bits will continue to be updated. The INT bit is cleared by a microprocessor read of the STATUS register. Document Version 1.0 page 10

11 $04:DETECTION orientation and shake detection parameters (write only) D7 D6 D5 D4 D3 D2 D1 D0 PD SHM SHTH[1] SHTH[0] SHC[1] SHC[0] ORC[1] ORC[0] PD = 1 powers down the DTOS to a non-functional low power state with a maximum current drain of 1 ua. ORC[1:0] sets the orientation count, which is the number of consecutive valid new orientation readings that must be made before a new orientation value is written into bits OR[1:0] in the STATUS register. The nominal rate at which readings are taken is 100 Hz. The number of consecutive valid orientation measurements required to effect a long-term orientation change is set by ORC[1:0] as follows: readings, readings, readings, readings. SHC[1:0] sets the shake count, which determines the number of readings allowed between the first shake event (perpendicular acceleration exceeding the threshold set by SHTH[1:0]) and the second shake event (acceleration breaking the threshold with opposite sign, SHM = 0, or just reversing sign, SHM = 1). The number of readings is set by SHC[1:0] as follows: readings, readings, readings, readings. SHTH[1:0] sets the shake threshold that the perpendicular acceleration must exceed to trigger the first shake event. The settings for SHTH[1:0] are: g, g, g, g. SHM is the shake mode bit. If SHM = 0, then for a shake to be detected, and written to SH[1:0] in the STATUS register, the second shake event must break the threshold set by SHTH[1:0] with the opposite sign of the first shake event, within the number of readings set by SHC[1:0]. If SHM = 1, then the second shake event must just have the opposite sign of the first shake event within the number of readings set by SHC[1:0]. Document Version 1.0 page 11

12 Device Marking Illustration Pin 1 Part number stands for MXC6225XU. Y= year 0= 2010 Lot number Week number in the year Figure 14 Document Version 1.0 page 12